1. Field of the Invention
The present invention relates generally to an improved electrode for use in electrical stimulation of patient muscle tissue for therapeutic purposes. More specifically, the present invention relates to an improved electrode for use with electronic heart pacers.
2. Description of Prior Art
Prior art electrodes are related to means for conducting electrical current to and from patient muscle tissue by contact between tissue and electrode at some uncontrollable, unspecified point or surface area of the electrode. Prior art electrodes normally are constructed to have smooth surfaces and are generally shaped in cylindrical-like configurations. Examples of prior art electrodes can be seen in U.S. Pat. Nos. 3,729,008 and 3,825,015. Background subject matter disclosed in these patents is incorporated herein by reference.
A shortcoming of prior art electrodes is that they cannot simultaneously solve two physiologically-related stimulation problems which confront devices which are employed to stimulate via electrodes. The first physiological constraint is that the stimulation threshold presented to a pacer electrode is directly proportional to electrode area in constant with patient tissue. In other words, the larger the contact area between heart tissue and electrode surface, the lower the current density and the higher the stimulation threshold. Thus, by reducing size of electrodes, current density can be increased.
However, polarization losses, the losses which are due to the build-up of charge at the interface between the tissue and the electrode surface and poled in a direction to oppose current flow, are inversely proportional to total electrode area. Therefore, if one designs an electrode to be small in surface area to achieve high current density, then the polarization losses may become excessive and prohibit efficient operation of a stimulating system. This has been and still is a problem of prior art electrodes.
The present invention provides a solution to this problem of the prior art. The present invention provides structure for simultaneously solving both problems, and is thereby a major advance over prior art electrodes.